K. A. Mauritz et al., Polym. Mater. Sci. Eng. 58, 1079-1082 (1988), in an article titled "Nafion-based Microcomposites: Silicon Oxide-filled Membranes", discuss the formation of micro composite membranes by the growth of silicon oxide microclusters or continuous silicon oxide interpenetrating networks in pre-swollen "NAFION.RTM." sulfonic acid films. NAFION.RTM. is a registered trademark of E. I. du Pont de Nemours and Company.
U.S. Pat. No. 4,038,213 discloses the preparation of catalysts comprising perfluorinated ion-exchange polymers containing pendant sulfonic acid groups on a variety of supports.
The catalyst utility of perfluorinated ion-exchange polymers containing pendant sulfonic acid groups, supported and unsupported has been broadly reviewed: G. A. Olah et al., Synthesis, 513-531 (1986) and F. J. Waller, Catal. Rev.-Sci. Eng., 1-12 (1986).
WO 95/19222 describes a porous microcomposite comprising a perfluorinated ion-exchange microcomposite containing pendant sulfonic acid and/or carboxylic acid groups entrapped within and highly dispersed throughout a network of metal oxide. These catalysts are differentiated from NAFION.RTM. supported catalysts in that by virtue of the preparation of the microcomposite catalyst, the polymer, in solution, becomes intimately mixed with a metal oxide network precursor in solution, and thus becomes thoroughly entrapped and highly dispersed throughout a resulting network of metal oxide. With the polymer being mechanically entrapped within the metal oxide network and not merely on the surface of a support, as is the case in supported catalysts, the catalytic activity of these microcomposites is significantly increased.
Although a variety of reactions can be beneficially catalyzed by the compounds and the composites cited above, there is still a need for catalysts of increased activity and selectivity and broader applications.